The present invention relates to an intelligent copier comprising an image sensor for deriving an image signal of a document to be copied and a printer for forming an image with the aid of the image signal.
Recently, as copiers developed, the amount of copies made has increased accordingly to a great extent and a variety of requirements for the copier arises. Generally, the requirements mentioned above are roughly classified into two groups such as decentralized processing for personal users by making the copier small and inexpensive and a batch processing by making it high performance and high speed. As for the high performance copier, functions such as image enlargement, reduction, synthesis, edition and color copy are required. In order to meet such requirements, there have been proposed intelligent copiers comprising a mass storage memory for storing image information.
For instance, the International Business Machine Company in the U.S.A. has developed an intelligent copier IBM 6670 and the Konishiroku Company, Iwatsu Company and Ricoh Company in Japan have developed the U-Bix Copier Printer, Iwatsu MG 6000 and Ricoh GT 1000, respectively. For example, the Ricoh GT 1000 comprises a laser beam printer and memory having a capacity of 256 KB and can perform three major functions, i.e., word processing, duplication and editing.
FIG. 1 is a schematic view showing one embodiment of a conventional intelligent copier. In the intelligent copier shown in FIG. 1, a document 1 is illuminated by an illumination lamp 2, and an image of the document thus illuminated is focused onto a sensor 4 through a projection lens 3. An output signal supplied from the sensor 4 is stored in a memory 7 through an interface 5, and a control unit 6 and a processed image with respect to the document 1 is printed out by a printer 8 under the control of the control unit 6. In the known intelligent copiers, use is made of a photo diode array, a CCD image sensor, an MOS image sensor, etc. as the sensor 4. Where a single photo diode element is used as the sensor 4, the document 1 is scanned by moving the sensor 4 two-dimensionally. Moreover, where a single photo diode array, or a CCD or MOS line image sensor is used, the document 1 is scanned by moving the image sensor one-dimensionally with respect to the document 1. Further, where a two-dimensional image sensor is used, the image sensor and the document 1 are fixed. In either case, the document 1 is scanned by the image sensor and the image information is stored in the memory 7 comprising a RAM or a frame memory.
In the known intelligent copier shown in FIG. 1, successive pixel signals of the document 1 are first stored in the memory 7 and then are supplied to the printer 8 after being suitably processed. In the duplication mode, the image signals are directly supplied to the printer 8 through the control unit 6, without storing them in the memory 7, in synchronism with the paper feed of the printer 8, a print head, a scanning of the document image, and so on. Therefore, it is possible to obtain a plurality of copies of the document 1 by storing the image signals of the document 1 in the memory 7 and then printing out a part or the whole of the pixel signals repeatedly, which are read out from the memory 7. Moreover, it is also possible to obtain an enlarged or a reduced copy by changing the pixel distance stored in the memory 7 by desired magnifications. Further, it is possible to obtain a partly erased copy by erasing a part of the image outside of the desired region stored in the memory 7, or by stopping a print-out of the printer 8 except for the desired region, and it is also possible to edit the image by erasing, changing or transferring the desired image region stored in the memory 7.
As mentioned above, the copy functions can be increased easily in a simple process, as compared with the known copier of an electrophotographic type, by storing the image information first in the memory 7. However, the amount of pixels stored in the memory 7 becomes 210.times.297.times.10.sup.2 =6,237,000 pixels per A4 size paper (210 mm.times.297 mm) if the resolution of the image is assumed to be 10 pixels/mm. Therefore, about 6.3 Mbit are required to obtain a black and white copy in which one pixel is assumed to be one bit, and the required amount is increased abruptly if making a gray level copy or a color copy. Thus, there is a drawback in that the whole copier becomes large in size and expensive in cost since the mass storage memory must be installed in the copier even if use is made of an IC memory or a magnetic disc, etc. as the memory 7.